<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>示例8</title>
</head>
<body>
    <script>
        function add(x=0,y=0){
            console.log(x,y,x+y)
        }

        add(4,8)
    </script>
</body>
</html>